In the related art, there is known a redundant calculation system having a redundant configuration including a plurality of operation units, each of which performs an interrupt process according to an external interrupt request (for example, refer to Patent Literature 1). In this redundant calculation system, each operation unit compares a counter value of a counter provided in the own operation unit with a count value of a counter provided in the other operation unit and corrects a cycle of the operation clock of the own operation unit according to the difference.